DE102011100105 discloses an internal gear pump comprising a pinion and a ring. The ring is arranged in a bore of a housing. A low-pressure space and a high-pressure space are located between the ring and the pinion. The high-pressure space is in fluid communication with a first pressure chamber forming a first angular extension of the bore of the housing on an outer peripheral surface of the ring. The purpose of the first pressure chamber is to modify the pressure field in the pump in order to reduce the clearance between the pinion teeth and the ring teeth in their contact region.
The first pressure chamber is arranged on slightly less than a quarter of the circumference of the ring. According to this document, placing the first pressure chamber so that it is radially adjacent to the low-pressure space allows the clearance between the pinion teeth and the ring teeth to be reduced.
One problem of the known internal gear pump is that the pressure field in the ring resulting from pressure differences causes a radial thrust from the ring towards the internal wall of the bore of the housing. Indeed, the pressure field pushes the ring towards the pinion in their contact region and thus also pushes the ring towards the internal wall of the bore in the radial extension of this contact region. This radial thrust causes friction and accelerated wear of the internal wall of the bore of the housing.